A review of proton exchange membranes modified with inorganic nanomaterials for fuel cells†

Abstract

This review gives an overview of the application of inorganic nanoparticles in the proton exchange membrane (PEM) of direct methanol fuel cells (DMFCs). The effects of the polymer membrane's physical and chemical characteristics after adding nanoparticles are covered. The article also covers how composite membranes can replace expensive, high-methanol-permeable, low chemically stable, and poor-conductive Nafion membranes at high temperatures. The different types of nanomaterials including solid, hollow, one-dimensional-(1D), two-dimensional-(2D) and three-dimensional-(3D) nanomaterials including clay-based composite membranes are discussed. Along with different types of nanoparticle composite membranes, different methods of making membranes such as dip coating, composite membranes and non-woven mats are also included in the article. The research shows that direct inclusion of the nanoparticles in the polymer as well as solution gel techniques require a precise ratio of the polymer and particles, blending time and a controlled drying temperature. The strong interactions of inorganic nanoparticles with polymers not only tune the pore structure of the proton exchange membrane for promoting Grotthuss and vehicular mechanisms but also create a link to hydrophilic functional groups that promote the further refining of these nanoparticles. The tortuous and non-swelled paths created with the inclusion of nanoparticles in the membrane minimize the methanol permeability while maintaining high proton conductivity. This paper also discusses the advancements in inorganic nanoparticle-modified membranes, their application and future improvements for their better application in the membrane of DMFCs.